1. Field of the Invention
The present invention relates to an anti-vibration support system for an engine wherein transmission of vibrations from an engine to a vehicle body frame is suppressed by controlling a supply of electric current to an actuator of an active anti-vibration supporting device.
2. Description of Related Art
An anti-vibration supporting device is disclosed in Japanese Patent Application Laid-open No. 7-42783. The disclosed anti-vibration supporting device varies a spring constant by applying electric current to an actuator to vibrate a movable member. The disclosed device exhibits effective anti-vibration performance in various ranges of engine rotational speed by previously storing a relationship between a peak current value and a phase of the applied electric current in a map to set the spring constant. Accordingly, an appropriate peak current value and phase of electric current to be applied to the actuator is obtained from the map, which corresponds to the engine rotational speed.
However, when an abnormality is generated in the engine during operation of the active anti-vibration supporting device and results in a sudden increase in the amount of vibration, the active anti-vibration supporting system is forced to operate in excess of a limit of the system's ability in an attempt to suppress the vibration. As a result, there exists a possibility an abnormality is generated in the active anti-vibration supporting system itself, or the durability of the active anti-vibration supporting system is decreased. In the case where an abnormality is generated in the active anti-vibration supporting system itself, if the operational state of the engine is switched to an operational state in which an amount or level of vibration is increased, the active anti-vibration supporting system may not be able to suppress the vibration, resulting in an increase of noise and/or the amount or level of vibration.